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Today I inserted another sim card in my fairphone 2. I want to use LTE with this card, but I wasn't able to configure 4G/3G/2G. 2G was selected and the button was disabled. So I just had 2G. The other card worked as expected and I was able to choose 4G/3G/2G. This bothered me the whole day.

LXC-Containers are very useful. They are more leightweight than virtual machines and not as static as docker-containers. That's why I like them especially for my server environments. In this article I will show a very basic setup of LXC-Containers on Debian Jessie.

Sometimes it is neccessary to filter packets based on their geo-ip location. Shorewall can make use of the xt_geoip-module for iptables. In this article I will explain how to setup this module on Debian.

We can use static ARP entries on hosts or routers to reduce ARP-traffic or to prevent ARP-spoofing. For such entries we need pairs of MAC-addresses and IP-addresses. The same information we also need for static DHCP-entries on a DHCP-server. Why not combine?

If someone attacks a linux-system, most administrator would block the ip-address of the attacker using iptables-rules. But there is another method to block the address of an attacker: nullroutes. A Nullroute simply directs to nowhere.